Over recent years the interest in semiconductor nanowires (NWs) has intensified. Nanowires are also referred to as nanowhiskers, nanorods and nanocolumns etc. For the purpose of this application the term nanowire is used for a nanostructure that include one-dimensional nanoelements, essentially in one-dimensional form, that are of nanometer dimensions in their width or diameter. Controlling the one-dimensional growth on the nanometer scale offers unique opportunities for combining materials, manipulating properties, both mechanical and electromagnetical, and to design novel devices.
For a large-scale impact of NW technology, a high level of compatibility with existing silicon processing will be essential. Advanced III-V heterostructure and high mobility NW components would then be available as an “add-on” technology for high speed electronics and photonics. However, as of today, the vast majority of reports on NW growth utilize the vapor-liquid solid (VLS) mechanism, see e.g. R. S. Wagner, In Whisker Technology, Levitt, A. P., Ed. Wiley: New York, 1970, and most commonly Au as catalyst material. It is well known that Au impurities in Si create deep levels acting as recombination centers degrading the electronic properties of the Si material. Thus, for compound nanowire technology to be compatible with silicon technology and processing, alternatives to Au need to be found.
Epitaxial growth of III-V semiconductors on Si presents several difficulties such as lattice mismatch, differences in crystal structure (III-Vs have a polar zincblende or wurtzite structure whereas Si has a covalent diamond structure), a large difference in thermal expansion coefficient and the formation of so called anti-phase domains. Much work has been done on planar growth of III-V materials on Si using different approaches attempting to grow device quality structures, see e.g. S. F. Fang et al., Gallium-Arsenide and Other Compound Semiconductors on Silicon. Journal of Applied Physics 68, R31-R58. (1990) for a review.
It is recognized that a III-V semiconductor NW grown out from an Si substrate would probably overcome several of the above mentioned problems, due to the small cross-section of the conjunction between the NW and the Si substrate. However, the known procedures for manufacturing NWs do, as described above, include Au-particles for catalyzing the growth process.